Barrel-shaped bearing

ABSTRACT

A barrel-shaped bearing which comprises an external ring and an internal ring, at least one row of barrel-shaped rolling bodies arranged therebetween, the cage in the form of a disk which turns together with the rolling bodies, engages inside a peripheral groove around each rolling body and is provided with recesses corresponding to the number of the rolling bodies of the one row arranged on the external periphery of the cage. The total rolling surface of the internal ring is embodied such that the cross section thereof is concave along the entire axial length of the rolling body. The smallest distance between both sides of the cavity of the disk-shaped cage in the area of the external periphery thereof is less than the diameter of a rolling body in the area of the peripheral groove thereof.

The invention is focused on a barrel-shaped bearing having an externalring and an internal ring, having at least one row of barrel-shapedrolling bodies arranged in between, and having at least one disk-shapedcage which revolves together with the rolling bodies, engages in anencircling groove of the rolling bodies of one row and, on its outercircumference, has a number of recesses corresponding to the number ofrolling bodies of a row.

An arrangement of the generic type can be seen in German patentspecification 663 179. This shows a spherical roller bearing, with therolling bodies having a stepped cross section and rolling with theirdistal regions on the external ring and their proximal regions on theinternal ring. However, in the case of this arrangement, first of all anunfavorable force profile is produced by the rolling bodies beingsubjected not only to compressive stress but also to bending stress, andsecondly, the axial space required by this bearing is comparativelylarge. However, the fact that, even if there is a small pivoting of theexternal ring in relation to the remaining bearing components, as ispossible in the case of barrel-shaped bearings, one of the two contactsurfaces between the rolling bodies and the outer ring can rapidly wearaway, is an even more serious disadvantage. Due to the transversemoments acting on the rolling bodies, this results in an instability ofthe relevant, barrel-shaped rolling body which may prevent the returnthereof, which is required during further rotation of the bearing, tothe running surface of the external ring and in such a case will lead tothe destruction of the bearing. Neither is the disk-type cage able toprovide any sort of stabilization here, since it guides the rollingbodies exclusively in the tangential position thereof, but not in theradial direction.

The disadvantages of the described prior art result in the probleminitiating the invention of developing a barrel-shaped bearing of thegeneric type in such a manner that, even if there is a considerablepivoting of the external ring relative to the remaining parts of thebarrel-shaped bearing, the rolling bodies can remain stable and, onfurther rotation of the bearing, can always return again to the centerof the running surface of the external ring.

This problem is solved in the case of the barrel-shaped bearing of thegeneric type by the entire running surface of the internal ring having aconcave cross section over the entire axial length of a rolling body;and by the smallest distance between the two sides of a recess of thedisk-type cage being smaller in the region of the outer circumferencethereof than the diameter of a rolling body in the region of the grooveencircling the latter.

These two measures complement each other insofar as, firstly, notransverse or tilting moments act on the rolling bodies because surfaceregions of the rolling bodies, which regions lie opposite one another inthe radial direction, conduct the radial forces to the two bearingrings, so that the rolling bodies remain stable even when the bearingcomponents pivot greatly. In addition, owing to the disk-shaped cage,the rolling bodies cannot become detached from the bearing even if theytemporarily lose complete contact with the external ring. The bearingaccording to the invention therefore operates satisfactorily even if thepivoting of the bearing components exceeds the customary limit values.

By the (greatest) width of the groove between the regions of therolling-body circumferential surface with the largest cross sectionmaking up only approximately one quarter to one tenth of the axialoverall length of the rolling body, a high (radial) load-bearingcapacity of a rolling body is produced, as a result of which abarrel-shaped bearing of this type is very stable in comparison with itsaxial extent.

It has proven favorable for the distance of the base of a recess of thedisk-type cage from the internal circumference thereof to be smallerthan the depth of the groove in a rolling body. As a result, thedesired, purely concave cross-sectional geometry of the running surfaceof the internal ring is possible.

By the maximum (radial) width of the annular disk-type cage beinggreater between the inner and outer circumferential circle thereof thanhalf of the diameter of a rolling body in the region of the grooveencircling of the latter, the rolling bodies can be engaged around atthe mutually diametrically opposite regions of the groove base and canthus be securely held even if the external ring is pivoted to a verygreat extent relative to the remaining bearing components.

The maximum (radial) width of the annular disk-type cage between theinner and outer circumferential circle thereof should preferably beequal to the diameter of a rolling body in the region of the grooveencircling the latter, or should be greater than said diameter, inorder, firstly, to be able to obtain sufficient stability despite therecesses on the external circumference and, secondly, to be able tosecurely engage around the individual rolling bodies.

It has proven successful to select the distance between two adjacentrecesses of the disk-type cage to be larger in the externalcircumference thereof than the difference of the maximum diameter of arolling body minus the diameter thereof in the region of the groovebase, for example by 5 to 30%, so that adjacent rolling bodies cannotcome into contact with one another.

If—as the invention furthermore provides—the sides of a recess in theregion of the external circumference of the disk-type case converge inthe radial direction thereof (as seen to the outside), then thefunctions of the smooth-running rotatability of the rolling bodies, onthe one hand, and the secure mounting thereof, on the other hand, arecombined with one another in an advantageous manner.

Further advantages arise from the fact that a recess of the disk-typecage is edged by a curve of constant curvature (in some regions). Theradius of curvature r_(S) of this curve should be somewhat larger thanhalf of the diameter of a rolling body in the region of the groove basethereof, so that a (small) play is ensured so that the relevant rollingbody can rotate in a smooth-running manner.

One effect of the form-fitting connection, which is required furtherabove, between the disk-type cage and rolling bodies is shown in thefact that the radius of curvature r (which is constant in some regions)of the edging curve of a recess of the disk-type cage should be smallerthan the radial width b of the disk-type cage: r<b, because in such acase the ends of the edge curve are able to approach one another in theregion of the external circumference of the disk-type cage.

A further advantageous feature of the invention resides in the fact thatthe encircling groove in the circumferential surface of a barrel-shapedrolling body has side surfaces which are mutually parallel or divergeoutward from each other. In order to ensure that the rolling bodiesrotate relative to the disk-type cage in a manner which is as free fromfriction as possible, the width of the groove in the circumferentialsurface of a barrel-shaped rolling body should be somewhat greater thanthe (axial) width d of the disk-type cage. On the other hand, inparticular load situations, individual rolling bodies can be forced intoa tilting movement in relation to the disk-type cage, and a movement ofthis type may, if appropriate, be facilitated by a groove shape havingoutwardly diverging side surfaces.

This feature of the invention can be developed to the effect that theside surfaces of the encircling groove in the circumferential surface ofa barrel-shaped rolling body run along conical circumferential surfaceareas. This is a simple geometrical shape which meets all of therequirements which have been set.

If, in this connection, the conical circumferential surface areas ineach case have opening angles a of less than 179°, then the sidesurfaces of a groove enclose an intermediate angle β=180°−a of more than2°. To a resultant rolling-body tilting angle is added a tilting anglecaused by the play between these elements, so that the maximum tiltingangle of the rolling-body axes of rotation in relation to theperpendicular to the area of the disk-type cage can be, for example, inthe order of magnitude of 5° to 10°. This play-induced tilting angle isinfluenced by the groove width b_(N) on the groove base. For reasonsconcerned with minimizing the friction, this value should correspond atleast to the (axial) thickness d of the disk-type cage; the differencebetween the groove width b_(N) at the groove base and the (axial)thickness d of the disk-type cage can preferably be set approximately tothe opening angle a of the groove side surfaces, which are in the shapeof a conical circumferential surface area, in accordance with thefollowing relationship:b _(N) −d≈2*r _(S)*tan(β/2)=2*r _(s)*tan(90°−a/2)

In such a case, those regions of the groove side surfaces of a rollingbody which extend approximately in the tilting direction are situated,in the maximum tilting position of said rolling body, approximatelyparallel to the disk-type cage, and guide forces which may have to betransmitted can be introduced over a large surface area and therefore atlow pressure.

On the other hand, the opening angle a of such conical circumferentialsurface areas should be more than 170°, preferably more than 175°, inparticular more than 178°, so that the side surfaces of a groove enclosean intermediate angle β=180°−a of less than 20°, preferably of less than10°, in particular of less than 4°. This results in an additionalguidance (with the effect of limiting the tilting angle) by the runningsurface of the external ring (for example as a consequence of the latterbeing greatly pivoted) of raised rolling bodies, which guidance requiresa picking up of contact between these elements in as problem-free amanner as possible (for example with the pivoting angle being reduced).

Finally, corresponding to the teaching of the invention, the crosssection of the internal ring and external ring and of the rolling bodiesis dimensioned in such a manner that a total of 3 or 4 contact pointsare produced per rolling body. This feature relates, in particular, tothe transverse radius of convexity of the cross-sectionally concaverunning surfaces of the internal ring and external ring. This radius ofconvexity should be somewhat larger than the radius of convexity of thebarrel-shaped rolling body within a longitudinal sectional plane throughthe relevant rolling body. Since, however, the groove of the barrel,which is intended for receiving the disk-type cage, runs in the regionof the “equator” of said barrel, the resulting two contact points cansplit into three or four contact points. This effect is desirablebecause the load-bearing force of a rolling body is increased as aresult, and can be further reinforced by the fact that the centralpoints of the transverse radii of convexity of the two barrel“hemispheres” are spaced apart from each other on both sides of the(equatorial) groove for the disk-type cage in the direction of the axisof rotation or symmetry of the relevant, barrel-shaped rolling body, butpreferably only by a small extent x, which, for example, is smaller thanthe groove width b_(N) at the groove base: x<b_(N).

Further features, details, advantages and effects on the basis of theinvention emerge from the description below of preferred embodiments ofthe invention and with reference to the drawing, in which:

FIG. 1 shows an end view of a barrel-shaped bearing according to theinvention;

FIG. 2 shows a section through FIG. 1 along the line II-II;

FIG. 3 shows an illustration corresponding to FIG. 2 with the radii ofconvexity plotted in;

FIG. 4 shows a perspective view of the barrel-shaped bearing from FIG.1, with the external ring having been partially broken up, so that theview of the rolling bodies held by the cage is opened up;

FIG. 5 shows an illustration corresponding to FIG. 4, with some of therolling bearings having been removed from the exposed cage;

FIG. 6 shows a side view of the circumferential surface of a rollingbody removed, according to FIG. 5, from the cage;

FIG. 7 shows an illustration corresponding to FIG. 6 of a modifiedembodiment of the invention;

FIG. 8 shows a plan view of a segment broken out of the cage from FIGS.4 and 5; and

FIG. 9 shows an illustration corresponding to FIG. 8 of an embodiment ofthe invention which has in turn been modified.

FIG. 1 shows a barrel-shaped bearing 1 according to the invention havingan external ring 2, an internal ring 3 and a row of barrel-shapedrolling bodies 4 which are arranged in between and are held atapproximately equidistant distances by an encircling cage 5.

Since the preferred barrel-shaped bearing is of single-row construction,the external ring 2 can be tilted relative to the remaining bearingcomponents 3 to 5. This is made possible by the fact that therolling-bearing running surface 6 on the external ring 2 has a concavecross section with a constant transverse radius of convexity.

During the tilting of the external ring 2 relative to the remainingbearing components 3 to 5, the cage 5 keeps the rolling bodies (4) intheir position. So that it does not, on the other hand, obstruct eitherthe tilting movement of the external ring 2 or the movement of therolling bodies 4, it extends through an encircling groove 7 of eachrolling body 4, as illustrated in FIGS. 2 and 3.

The cage 5 can be produced from a disk with a constant thickness d, forexample can be punched out of a metal sheet. As FIG. 8 shows, a numberof recesses 9 corresponding to the number of rolling bodies 4 are cutout of an annular basic structure with a constant, radial width from theradially outer circumference 8. These recesses each accommodate onerolling body 4.

The internal circumference 10 of the disk-shaped cage 5 preferablycorresponds to the maximum external circumference of the internal ring3, in particular at an edge 11 of the running surface 12 thereof, sothat the cage 5 can easily be pulled over the internal ring 3, forexample mechanically. The insertion of the rolling bodies 4 into therecesses 9 of the disk-shaped cage 5 can likewise be brought aboutautomatically, the inserted rolling bodies 4 then being held in situbecause they are engaged around in the region of the relevant groovebase 13 by the cage 5. After the external ring 2 has been pulled overinto a position tilted, for example, by 90° and has been pivoted intothe plane of the internal ring 3, the assembly of the barrel-shapedbearing 1 is finished.

The barrel-shaped rolling bodies 4 are therefore divided approximatelycentrally between their two end sides 14 in their “equatorial” planeinto two halves 15, as it were into “hemispheres” by the encirclinggroove 7. In the case of the rolling bodies 4 according to theinvention, the two contact regions of a bearing with undivided (notgrooved) rolling bodies are therefore divided into four contact regions.This affords the advantage that the radial loads which are to betransmitted are distributed over a relatively large overall area.

This effect is therefore additionally assisted by the two “hemispheres”15 of a rolling body 4 being split into different cross-sectionalgeometries. To be precise, one cross section through the circumferentialsurface area 16 of a rolling body has in both hemispheres 15 thereof arespective profile in the form of an arc of a circle with preferablyidentical radii of curvature r_(T). However, the central points 17, 18of the cross-sectional curvature of the two hemispheres do not coincide,but rather are slightly offset from each other in the axial direction ofthe barrel-shaped bearing 1, to be precise toward the relevantrolling-body hemisphere 15 or end side 14. A value of the order ofmagnitude of 0.001 to 0.02, in particular of between 0.002 and 0.01, hasproven successful as the “offset factor” k_(V)=x/r_(T).

Since, in addition, the radii of curvature r_(A), r₁ of the runningsurfaces 6, 12 of the external ring and internal ring 2, 3 are selectedto be somewhat larger than the radii of curvature r_(T) of the tworolling-body hemispheres 15, in the ideal state two mutuallydiametrically opposite contact regions of the external ring 2, on theone hand, and the internal ring 3, on the other hand, are produced oneach hemisphere 15. As a measure of the deviations of the radii ofcurvature r_(A), r₁, r_(T), the “osculating factors” k_(A), k₁ can bespecified. The latter are defined ask _(A·)=(r _(A) −r _(T))/r _(T) =y/r _(T)k _(1·)=(r ₁ −r _(T))/r_(T).

These osculating factors k_(A), k₁ are preferably to be in the order ofmagnitude of 0.01 to 0.1, in particular of between 0.02 and 0.05.

Since the central point 19 of cross-sectional curvature of the runningsurface 6 of the external ring 2 lies on the axis of rotation orsymmetry 20 thereof, to be precise on the central base plane thereof,the central points 17, 18 of cross-sectional curvature of thecircumferential surface areas 16 of the two rolling-body hemispheres 15are in each case offset radially outward by y from the axis of rotation20 and are offset in relation to the central base plane toward therelevant end side 14 by x/2.

It can be seen in FIG. 4 that even if the external ring 2 is brokenaway, the rolling bodies 4 are held in situ by the cage 5. This isachieved by the form-fitting connection of the recesses 9 of the cage 5with the groove regions 7 of the rolling bodies 4.

Two possible groove shapes are illustrated in FIGS. 6 and 7: in the caseof the embodiment according to FIG. 6, the groove 7 has planar sidesurfaces 21, that are produced, for example, by means of a straightplunge cut. Accordingly, the width b_(N) of the groove 7 isapproximately constant. The groove base 13 follows a cylindricalcircumferential surface area with the radius of curvature r_(N). Thetransition regions between the groove base 13 and groove side surfaces21, between the latter and the circumferential surface areas 16 andbetween the circumferential surface areas 16 and end surfaces 14 arerounded in order to avoid burrs and stress concentrations.

The embodiment of a rolling body 22 according to FIG. 7 differs fromthat according to FIG. 6 exclusively by virtue of the fact that thegroove side surfaces 23 run along conical circumferential surface areas.This involves very blunted cones having preferably identical openingangles a of virtually 180° in each case (for example 170° to 179°).Accordingly, the groove side surfaces 23 diverge from each other at anangle β, as viewed along a radial plane to the outside from the axis ofsymmetry 24. In this case: β=(180°−a) in the case of identical openingangles a of both groove side surfaces 23, and in the case of differentopening angles a₁, a₂: β=(180°−(a₁+a₂)/2). The (axial) width of thegroove base is in turn b_(N) and its radius of curvature is r_(N). Withthe same values for b_(N) and d, this embodiment tolerates relativelylarge offset angles of the barrel-shaped rolling bodies 22 and thereforeresults in a smaller amount of wear when subjected to correspondingstresses.

A cutout from the cage 5 is reproduced in FIG. 8. Recesses 9 which arein the form of an arc of a circle and have a constant radius ofcurvature r_(S) can be seen. By means of r_(S)>r_(N) and d<b_(N), arotational movement of the rolling bodies 4, which is as free aspossible from friction, in relation to the cage 5 is ensured. In orderto be able to secure the rolling bodies, the circumference 25 of arecess 9 extends over an arc of a circle of more than 180°, for exampleof between 200° and 230°, in particular of 210° to 220°, so that the endregions 26 of the recess circumference 25 converge, in the viewingdirection from the internal circumference 10 of the cage 5 towards itsexternal circumference 8. The minimum distance of the end regions 26 issmaller than the diameter (2*r_(N)) of the rolling bodies 4 in theregion of the groove base 13, so that the rolling bodies 4 are engagedaround in a form-fitting manner. In order to release a rolling body 4from the cage 5, the former has therefore to be pulled outward with alarge force in order (temporarily) to push the end regions 26 of therecess circumference 25 apart. The end regions 26 therefore form snap-inlugs for snapping in the rolling bodies 4.

The modified disk-type cage 27 from FIG. 9 has a similar effect. Thiscage differs from the cage 5 according to FIG. 8 exclusively by therecess circumference 28, which has the radius of curvature r_(S) in itsregion 29 facing the inside 10 of the cage 27, having, approximatelylevel with its radial profile, flattened (approximately mutuallyparallel) regions 30 (having a length l, of for example r_(S)/3) whichare then adjoined by the actual snap-in lugs 31, which are in turncurved and converge towards each other and the radius of curvature ofwhich can be selected to coincide with r_(S). This embodiment toleratesrelatively large radial offsets of the cage 27 with respect to therolling bodies 4, which offsets may occur, for example, as a consequenceof sharp temperature fluctuations, but without the rolling bodies 4being able to be released if the external ring 2 tilts sharply. As inthe case of the cage 5, the edges of the recess circumference 32 arealso cross-sectionally rounded here.

1. A barrel-shaped bearing comprising: an external bearing ring, and aninternal bearing ring inward of the external ring; at least one row ofbarrel-shaped rolling bodies arranged between the external and internalrings, each rolling body, having opposite ends and an encircling grooveinto and extending around the rolling body between the ends thereof; atleast one disk-shaped cage between the rings which revolves togetherwith the rolling bodies, the cage engages in the encircling grooves ofthe rolling bodies of one row, the cage having an outer circumference,including a number of recesses therein corresponding to the number ofrolling bodies in the row, the inner ring having a running surfacetoward the rolling bodies, and the entire running surface of theinternal ring has a concave cross section extending axially over theentire axial length of the rolling bodies; the recesses in the cagebeing of such depth and so shaped as to have two opposed sides such thatthe smallest distance between the two sides of a recess of the disk-typecage is smaller in the region of the outer circumference of the cagethan a diameter of a rolling body in the region of the groove encirclingthe rolling body.
 2. The barrel-shaped bearing as claimed in claim 1,wherein the maximum radial width b of the annular disk-type cage betweenthe outer and an inner circumferential surface of the cage is greaterthan half the diameter of a rolling body in the region of the grooveencircling the rolling body.
 3. The barrel-shaped bearing as claimed inclaim 1, the maximum radial width b of the annular disk-type cagebetween the outer and an inner circumferential circle thereof is equalto or greater than the diameter of a rolling body in the region of thegroove encircling the rolling body.
 4. The barrel-shaped bearing asclaimed in claim 1, wherein the distance between two adjacent ones ofthe recesses in the disk-type cage in the region of the outercircumference thereof is greater than the difference in the maximumdiameter of a rolling body minus the diameter of the rolling body in theregion of the groove base.
 5. The barrel-shaped bearing as claimed inclaim 1, wherein opposing sides of a recess of the disk-type cage in theregion of the outer circumference of the cage converge in the radialdirection.
 6. The barrel-shaped bearing as claimed claim 1, wherein arecess in the disk-type cage is edged by a curve of constant curvaturer_(S) at least in some regions.
 7. The barrel-shaped bearing as claimedin claim 1, wherein the radius of curvature r_(S) of an edging curve ofa recess of the disk-type cage is smaller than a radial width b of thedisk-type cage: such that r_(S)<b.
 8. The barrel-shaped bearing asclaimed in claim 1, wherein the encircling groove in the circumferentialsurface of a barrel-shaped rolling body has mutually parallel sidesurfaces or has side surfaces that diverge outward from each other. 9.The barrel-shaped bearing as claimed in claim 8, wherein the sidesurfaces of the encircling groove in the circumferential surface of abarrel-shaped rolling body run along conical circumferential surfaceareas.
 10. The barrel-shaped bearing as claimed in claim 9, wherein theconical circumferential surface areas of a groove have opening angles aof more than 170°, so that the side surfaces of a groove enclose anintermediate angle β of less than 20°.
 11. The barrel-shaped bearing asclaimed in claim 9, wherein the conical circumferential surface areashave opening angles a of less than 179°, so that the side surfaces of agroove enclose an intermediate angle β of more than 2°.
 12. Thebarrel-shaped bearing as claimed in claim 1, wherein the groove haswidth b_(N) at the groove base which corresponds approximately to thethickness d of the disk-type cage.
 13. The barrel-shaped bearing asclaimed in claim 1, wherein the external ring, the internal ring and therolling bodies have respective cross-sections dimensioned such that atotal of three or four contact points with the rings are produced perrolling body.
 14. The barrel-shaped bearing as claimed in claim 10,wherein the opening angle is more than 175° and the intermediate angleis less than 10°.
 15. The barrel-shaped bearing of claim 10, wherein theopening angle is more than 178° and the intermediate angle is less than4°.